I just bought a iPhone 6 and the Internet reception is very poor and I think it's the phone.

I know this sounds too easy, but I would start with resetting/force restarting the phone. Hold down on the sleep and home buttons at the same time for about 10-20 seconds until the Apple logo appears on the screen. See if that does any good.

AAre you basing theses results on your home WiFi network only? If you are, I will also try power cycling your router. I realize that your other devices can connect, but it is worth a try. Just unplug you router for about 30 seconds and then plug it back in again.

You could also try Settings>General>Reset>Reset Network Settings. You will have to enter your WiFi network password again.

I would take it back to where you bought it and test it there.

That sounds like a possibility.

Good luck!

One other test you could do is to try it at a public Wi-Fi like a coffee shop and see if you experience the same behavior. If you do then it is not your own Wi-Fi or router - time for the Apple Store or where ever you bought it from. Good luck.

Not that you need another opinion at this point, but I agree with Philly, take the phone back and try it there. If it doesn't work correct,y, ask for a replacement.